The study, which was published in a recent issue of Psychological Science, looked at how the use of language on Twitter could predict the prevalence of heart disease in a community. For the study, researchers from the University of Pennsylvania, Northwestern University, and the University of Melbourne analyzed tweets and compared them to heart disease risk. They found that tweets are a better predictor of heart disease in an area than factors such as smoking, diabetes, income and obesity.

To get their data, researchers looked back at public tweets that had been geo-tagged (to show the user's location,) from 2009-2010. They then sorted the tweets using word filters and algorithms into those that revealed negative emotions — such as hate, fatigue, hostility and stress — and those that were more positive, showing optimism, opportunity or ambition. Then, the researchers compared this data with coronary heart disease death rate numbers from the Centers for Disease Control and Prevention.

They found that the tweets that were heavy with negative emotion also correlated with areas where there is a high risk for heart disease, whereas positive tweets were linked to lower levels. What's interesting is that the Twitter users themselves are not the same people in the community being diagnosed with heart disease — they are far too young. But researchers think that the tweets point to the negative stress felt by the community at large, and this stress could be contributing to the higher rates of heart disease.

This isn't the first time that researchers have used social media data to track public health trends. A recent Washington Post article pointed out that health experts have clued in to using Twitter to track the flu, for example. The beauty of using Twitter in a study such as this heart disease predictor is two-fold. For starters, the data on Twitter is instantaneous and continuous; researchers don't have to set up complicated surveys for participants to complete. In addition, it provides a more honest view of a person's outlook and feelings than they might provide on a survey.

"Twitter is where people talk about themselves, where they express their emotions candidly," said Johannes Eichstaedt, a psychological scientist at University of Pennsylvania. Eichstaedt and his team hope that health experts can use this information to develop better diagnostic and treatment options for heart disease.